Spine Width

{
  "asOf": "2026-10-12T01:40:25.937Z",
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "inchesPerPage": 0.002252,
  "knownPapers": {
    "color": 0.002347,
    "cream": 0.0025,
    "white": 0.002252
  },
  "notChecked": [
    "your printer's own cover template, which is the only authority (factors vary by printer, paper stock and year)",
    "hardcover boards, which add their own thickness",
    "…1 more"
  ],
  "pages": 300,
  "paperUsed": "white",
  "reasons": [
    "Spine = pages x 0.002252 in per page (black ink on white paper (common POD figure 0.002252 in per page)).",
    "These are common published print-on-demand figures; they vary by printer, so confirm with your printer's cover calculator before ordering."
  ],
  "source": "computed locally (spine = pages x paper thickness per page; common published POD factors)",
  "spineWidthIn": 0.6756,
  "spineWidthMm": 17.16,
  "summary": "300 pages on white paper give a spine of about 0.6756 in (17.16 mm).",
  "verdict": "COMPUTED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://publishing-calc.x402tookit.com/spine-width?pages=300&paper=white'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://publishing-calc.x402tookit.com/spine-width?pages=300&paper=white' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fpublishing-calc.x402tookit.com%2Fspine-width
const res = await pay("https://publishing-calc.x402tookit.com/spine-width?pages=300&paper=white");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://publishing-calc.x402tookit.com/spine-width?pages=300&paper=white")
    print(res.status_code, res.text)